1. Technical Field
The present invention concerns a safety arrangement for hoists having a hoist cage adapted to travel in a path in a hoist shaft. The arrangement secures safety zones in case persons should be outside the hoist cage in the hoist shaft.
2. Description of the Background Art
Demands on safety zones above and below hoist cages have been made more stringent during recent years and further restrictions are expected. These new demands can usually be met by new installations but increasing the depth and/or raising the roof on existing hoist shafts is often impossible in practice.
These conditions have resulted in the use of known technology to create solutions in which electronic control systems for hoists interact with some form of mechanical safety device, often in the form of manual extendable support being arranged to abut either the hoist cage directly or particular surfaces on the hoist cage through inelastic engagement.
For example, WO 99/47447 illustrates an arrangement in which the mechanical safety device comprises a tilting support, which in a tilted down passive position is located flat on the shaft floor, allowing normal hoist cage operation, and in a tilted up active vertical position has its free upward facing end intended to abut against a downward moving hoist cage, thereby ensuring a safety zone and putting the hoist in a second operating position for service and maintenance. The position of the support must be changed manually by the operator from inside the shaft.
It would be preferable to have guaranteed safety zones in all situations where it is possible for a person to enter the shaft outside the hoist cage for service, maintenance, repair, inspection, forced entry, etc. To guarantee this state, it should be virtually impossible to enter the hoist shaft outside the hoist cage without the hoist being in position for service and the safety zone being secured.
One object of the present invention is to alleviate or even overcome the aforesaid failings in known techniques.
These and other objects, distinctive features and advantages with the invention will be evident in the dependent patent claims and the following detailed description of a preferred embodiment of the invention. This embodiment constitutes a specimen and accordingly does not limit the scope of protection of the invention.